Breast cancer risk linked to dense tissue.

Breast cancer risk linked to dense tissue

Women with a higher percentage of dense breast tissue face a greater risk of developing breast cancer than women with primarily fatty breasts, according to new research presented this week at the American Cancer Society's 31st Science Writers' Seminar held in Irvine, Calif. The research team developed and tested a technique that measures the amount of dense tissue picked up by mammograms, X-ray pictures of the breast.

The method may provide doctors with a simple, accurate way to identify women with a higher-than-average threat of breast cancer, a disease that will strike about 142,000 women in the United States this year.

"We believe that the measurement of percent densities is a promising technique that could enhance the physician's ability to identify high-risk groups of women," says Audrey F. Saftlas, an epidemiologist at the Centers of Disease Control in Atlanta. Saftlas, John N. Wolfe at the Hutzel Hospital in Detroit and colleagues began their work with the theory that cancer occurs more often in women whose breasts contain proportionally more dense-type tissues, such as epithelial and connective tissue, because breast cancers occur most often in these cells.

To test their idea, they studied 567 women enrolled in the Breast Cancer Detection and Demonstration Project, a nationwide, five-year screening program sponsored by the American Cancer Society and the National Cancer Institute. Wolfe used an instrument called a planimeter to determine the percentage of dense tissue highlighted by each woman's initial mammogram. The researchers found that the 266 women diagnosed with breast cancer during the project's fifth year were more likely to have more dense breast tissue that 301 women who showed no signs of breast cancer during the study period.

"We found that breast cancer risk increased steadily with increasing breast density," Saftlas reports. Women whose mammograms showed over 65 percent dense tissue developed breast cancer at a rate more than 400 percent higher than that of women with densities of less than 5 percent. Women with densities of 5 to 25 percent developed the disease at a 70 percent higher rate compared with the same group, Saftlas says.

Women with a family history of breast cancer faced an even greater threat: Those who reported breast cancer in a mother, daughter or sister and who showed mammographic densities of 45 percent or more developed breast cancer at a rate 700 percent higher than that of women with no family history and a mammographic density of less than 5 percent, Saftlas says.

The study is important because doctors need a more accurate method of spotting women at risk of breast cancer to provide early detection, says Benjamin F. Byrd Jr., clinical professor of surgery at Vanderbilt University in Nashville, Tenn. Still, the new technique's accuracy must be verified, Byrd adds. Saftlas agrees, but expects further research will confirm the new findings. "The percentage of the breast containing mammographic densities is a bona fide risk factor for breast cancer that is at least as important as family history," she says.